It would appear that when QCAD imports a DXF, it reorders the layers into alphabetical order (at least when importing R2011). I have not tested this extensively but on other programs, the order is different from alphabetical. Ideally the operator should be given a choice to order the layers as exported (assuming the DXF format remembers that) or alphabetical. This is because a drawing may have a certain stack up of layers (like a printed circuit board) and then alphabetic ordering is not useful nor desired.